1. Field of the Invention
Embodiments of the present invention relate to an injection apparatus, system, and method. In particular, embodiments of the present invention relate to an injection station and an injection tooling of an injection blow molding machine for use in high cavitation applications.
2. Description of the Related Art
Injection blow molding is a technique used for creating various containers such as plastic bottles. The injection blow molding process is performed with an injection blow molding machine that first injection molds a resin into a plurality of parisons of desired shapes and then blow molds the parisons into the final molded articles.
An injection station of the injection blow molding machine typically includes a split parison mold assembly that defines a plurality of cavities within which parisons are formed. Hot melt resin injection nozzles have nozzle gate inserts that are seated in gate openings of the cavities for injecting resin into the cavities so as to form the parisons. To remove a set of newly formed parisons from the mold, an upper mold half is raised off a bottom mold half, and cores that carry the new parisons are then lifted and rotated out of the mold. A new set of cores is placed in the cavities of the bottom mold half and the mold is closed, creating a diametrical sealing relationship between each tip of the nozzle gate insert and the wall of its gate opening and preparing the mold cavities to receive hot melt resin through the nozzles.
Each nozzle is coupled, at its base, with a resin manifold that is secured to a die plate via a base plate. Prior to performing the injection blow molding, the manifold is heated to a desired operating temperature. Hot melt resin is supplied to each nozzle at the nozzle's base from a resin source associated with the manifold. The resin then flows through the nozzles and to the parison mold. In certain tooling applications, such as tooling described in U.S. Pat. No. 7,771,189 (the '189 patent) filed on Mar. 3, 2008, and entitled “INJECTION MOLDING APPARATUS WITH REPLACEABLE GATE INSERT,” which is incorporated by reference herein in its entirety, a gap of between 0.000 and 0.010 inches (hereinafter, a “gap” or a “zero gap”) may exist between the inside of the nozzle gate insert and the front end of the nozzle to allow independent movement of the cavities and the manifold. Such movement may arise due to the difference in thermal expansion of the cavities and the manifold since the cavities and the manifold may be operated at different temperatures. As such, hot melt resin will fill the gap and be cooled down enough to form a seal during injection of the hot melt resin into the cavity. However, the holt melt resin that collects within the gap can cause significant hydraulic backpressure against the nozzle and the resin manifold. Especially in injection tooling applications that use a plurality of nozzles to form a plurality of parisons, such hydraulic backpressures may exert forces in excess of thirty tons on the resin manifold and/or on the base plate. Such a force can cause the resin manifold and/or the base plate to move backward, to bend upward, and/or to bow, thus causing the gap to increase and eventually causing resin to leak from the interface of the nozzle gate insert and the front end of the nozzle.
As mentioned, before the nozzles can inject the hot melt resin into the cavities, the hot melt resin is required to be heated to a beginning operating temperature (e.g., between 350 to 560° F.). Additionally, the resin must maintain at least an injection operating temperature while being transferred through and injected from the manifold. Such an injection operating temperature is maintained using heat supplied to the injection tooling components by external sources. However, any heat applied to the resin manifold and/or the base plate tends to cause the manifold and/or base plate to deform, such as by bending or bowing. Such deformations make it difficult to maintain the zero gaps, especially in a high cavitation mold.
Thus, it would be desirable to have an injection station of an injection blow molding machine that is configured to maintain a resin manifold securely in place during operation, even with the presence of hydraulic forces between every nozzle gate insert and corresponding front end of the nozzle.